Exhaust system for outboard motor

Abstract

An exhaust system for an outboard motor includes an improved construction that can be compact enough for the limited space afforded within a powerhead of an outboard motor. The outboard motor includes an engine and a support member arranged to support the engine. The engine includes a cylinder block that defines a plurality of cylinder bores. The cylinder bores extend generally horizontally and spaced apart vertically from each other to form a cylinder bank extending generally vertically. At least two exhaust manifolds extend generally vertically aside and along the cylinder bank. Pistons reciprocate within the cylinder bores. A cylinder head closes ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons. The cylinder head further defines at least one exhaust port per each one of the combustion chambers. Exhaust passages communicate with the exhaust ports. The exhaust passages are coupled with the exhaust manifolds so that at least one of the exhaust passages is allotted to each one of the exhaust manifolds.

What is claimed is:  
     
       1. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, the cylinder bores extending generally horizontally and spaced apart vertically from each other to form a cylinder bank, the cylinder block further defining first and second exhaust manifolds extending generally vertically along side the cylinder bank, the first exhaust manifold being interposed between the cylinder bank and the second exhaust manifold, pistons reciprocating within the cylinder bores, and a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with one of the combustion chambers through at least one of the exhaust ports, at least one of the exhaust passages being connected to the first exhaust manifold, at least another one of the exhaust passages being connected to the second exhaust manifold, a top of the first exhaust manifold being positioned higher than a top of the second exhaust manifold. 
     
     
       2. The outboard motor as set forth in  claim 1 , wherein the cylinder bank has a generally vertical central plane and the first and second exhaust manifolds extend generally in parallel to the central plane. 
     
     
       3. The outboard motor as set forth in  claim 1 , wherein the first and second exhaust manifolds are configured so as to join together at a location lower than the lower-most cylinder bore. 
     
     
       4. The outboard motor as set forth in  claim 3 , wherein the first exhaust manifold includes a detour section communicating with one of the exhaust passages and with a downpipe section of the exhaust manifold. 
     
     
       5. The outboard motor as set forth in  claim 4 , wherein the exhaust passages and the first and second exhaust manifolds together define a plurality of exhaust paths, each one of the exhaust paths extends from one of the exhaust passages to a location where the first and second exhaust manifolds merge together, and the exhaust passages and the first and second exhaust manifolds are configured such that the lengths of the plurality of exhaust paths are generally equal to one another. 
     
     
       6. The outboard motor as set forth in  claim 1 , wherein the engine additionally includes an ignition system configured to fire the respective combustion chambers in a preset order, and the exhaust passages associated with the combustion chambers which have consecutive firing orders are arranged to communicate with different ones of the first and second exhaust manifolds. 
     
     
       7. The outboard motor as set forth in  claim 1 , wherein the engine additionally includes exhaust valves arranged to selectively open and close the exhaust ports. 
     
     
       8. The outboard motor as set forth in  claim 7 , wherein the exhaust passages associated with the exhaust valves, which do not open consecutively, are allotted to the same exhaust manifold. 
     
     
       9. The outboard motor as set forth in  claim 1 , wherein the cylinder bores and the first and second exhaust manifolds have end openings facing in the same direction, and the cylinder head is coupled with the cylinder block in a manner cooperating with the end openings. 
     
     
       10. The outboard motor as set forth in  claim 1 , wherein at least two exhaust passages are connected to the first exhaust manifold, each one of the at least two exhaust passages is generally equal in length to one another. 
     
     
       11. The outboard motor as set forth in  claim 10 , wherein at least other two exhaust passages are connected to the second exhaust manifold, each one of the at least other two exhaust passages is generally equal in length to one another. 
     
     
       12. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, the cylinder bores extending generally horizontally and spaced apart vertically from each other to form a cylinder bank, the cylinder block further defining at least two exhaust manifolds extending generally vertically along side the cylinder bank, pistons reciprocating within the cylinder bores, and a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, at least one of the exhaust passages being connected to the exhaust manifolds so that at least one of the exhaust passages is allotted to each one of the exhaust manifolds, and a crankshaft coupled to the pistons and journaled for rotation about a crankshaft axis, the cylinder bank and the crankshaft being arranged such that a first plane, which contains the crankshaft axis, lies parallel to and offset from a second plane, which contains axes of the cylinder bores, the first plane being offset to a side of the second plane on which the exhaust manifolds are disposed. 
     
     
       13. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, first and second exhaust manifolds extending next to the cylinder bores, the first exhaust manifold being interposed between the cylinder bores and the second exhaust manifold, the first exhaust manifold being longer than the second exhaust manifold, pistons reciprocating within the cylinder bores, and a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, at least one of the exhaust passages communicating with the first exhaust manifold, at least another one of the exhaust passages communicating with the second exhaust manifold, and the first exhaust manifold including a manifold section and a detour section that lies between one of the exhaust passages and the manifold section. 
     
     
       14. The outboard motor as set forth in  claim 13 , wherein the exhaust passages and the first and second exhaust manifolds together define a plurality of exhaust paths, each exhaust path extends from a respective exhaust passage to a location where the first and second exhaust manifolds merge together, and the exhaust passages and the first and second exhaust manifolds are configured such that the lengths of the plurality of exhaust paths are generally equal to one another. 
     
     
       15. The outboard motor as set forth in  claim 13 , wherein the engine additionaly includes an ignition system firing the respective combustion chambers in a preset order, and the exhaust passages associated with the combustion chambers which have consecutive firing orders communicate with different ones of the first and second exhaust manifolds. 
     
     
       16. The outboard motor as set forth in  claim 13 , wherein the cylinder bores and the first and second exhaust manifolds have end openings facing in the same direction, and the cylinder head is coupled with the cylinder block so as to cooperate with the end openings of the cylinder bores and the first and second exhaust manifolds. 
     
     
       17. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, the cylinder bores being disposed in line to form a cylinder bank, at least two exhaust manifolds, the respective exhaust manifolds extending along side the cylinder bank, pistons reciprocating within the cylinder bores, and a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, the exhaust passages communicating with the exhaust manifolds so that at least one of the exhaust passages is connected to each one of the exhaust manifolds, at least one of the exhaust manifolds including a downpipe section and a detour section that lies between one of the exhaust passages and the downpipe section, and the exhaust manifold that includes the detour section being interposed between another one of the exhaust manifolds and the cylinder bank. 
     
     
       18. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, at least two exhaust manifolds, pistons reciprocating within the cylinder bores, and a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, the exhaust passages communicating with the exhaust manifolds so that at least one of the exhaust passages is connected to each one of the exhaust manifolds, at least one of the exhaust manifolds including a downpipe section and a detour section that lies between one of the exhaust passages and the downpipe section, the detour section including a vertical jog. 
     
     
       19. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, at least two exhaust manifolds, pistons reciprocating within the cylinder bores, and a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, the exhaust passages communicating with the exhaust manifolds so that at least one of the exhaust passages is connected to each one of the exhaust manifolds, at least one of the exhaust manifolds including a downpipe section and a detour section that lies between one of the exhaust passages and the downpipe section, the detour section being defined at least in part by a baffle. 
     
     
       20. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, at least two exhaust manifolds, pistons reciprocating within the cylinder bores, a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, the exhaust passages communicating with the exhaust manifolds so that at least one of the exhaust passages is connected to each exhaust manifold, at least one of the exhaust manifolds including a downpipe section and a detour section that lies between one of the exhaust passages and the downpipe section, and a crankshaft coupled to the pistons and journaled for rotation about a crankshaft axis, the cylinder bores and the crankshaft being arranged such that a first plane, which contains the crankshaft axis, lies parallel to and offset from a second plane, which contains axes of the cylinder bores, the first plane being offset to a side of the second plane on which the exhaust manifolds are disposed. 
     
     
       21. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores, the cylinder bores extending generally horizontally and spaced apart from each other to form a cylinder bank, the cylinder block further defining at least two exhaust manifolds, pistons reciprocating within the cylinder bores, a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each one of the combustion chambers having at least one of the exhaust ports, each one of the exhaust passages communicating with each one of the combustion chambers through at least one of the exhaust ports, the exhaust passages being connected to the exhaust manifolds so that at least one of the exhaust passages is allotted to each one of the exhaust manifolds, the exhaust manifolds being coupled together at a location lower than the lower-most cylinder bore, and a crankshaft coupled to the pistons and journaled for rotation about a crankshaft axis, the cylinder bores and the crankshaft being arranged such that a first plane, which contains the crankshaft axis, lies parallel to and offset from a second plane, which contains axes of the cylinder bores, the first plane being offset to a side of the second plane on which the exhaust manifolds are disposed. 
     
     
       22. The outboard motor as set forth in  claim 21 , wherein one of the exhaust manifolds is interposed between the cylinder bank and another one of the exhaust manifolds. 
     
     
       23. The outboard motor as set forth in  claim 21 , wherein the exhaust manifolds extend into the support member and join together within the support member. 
     
     
       24. The outboard motor as set forth in  claim 21 , wherein the engine additionally includes an ignition system firing the respective combustion chambers in a preset order, and the exhaust passages associated with the combustion chambers which have consecutive firing orders communicate with different ones of the exhaust manifolds. 
     
     
       25. The outboard motor as set forth in  claim 21 , wherein the cylinder bores and the exhaust manifolds have end openings facing in the same direction, and the cylinder head is coupled with the cylinder block in a manner cooperating with the end openings. 
     
     
       26. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores disposed in line to form a cylinder bank, the cylinder block further defining at least two exhaust manifolds extending aside the cylinder bank, pistons reciprocating within the cylinder bores, a cylinder head closing ends of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining a plurality of exhaust ports and a plurality of exhaust passages, each combustion chamber having at least one exhaust port, and each exhaust passage communicating with a respective one of the combustion chambers through at least one of the exhaust ports, the exhaust passages communicating with the exhaust manifolds so that at least one of the exhaust passages is connected to each exhaust manifold, and a crankshaft coupled to the pistons and journaled for rotation about a crankshaft axis, and the cylinder bores and the crankshaft being arranged such that a first plane, which contains the crankshaft axis, lies parallel to and offset from a second plane, which contains axes of the cylinder bores, the first plane being offset to a side of the second plane on which the exhaust manifolds are disposed. 
     
     
       27. The outboard motor as set forth in  claim 26  additionally comprising a protective cowling arranged to surround the engine, the protective cowling having a longitudinal center plane extending vertically, wherein the first plane and the longitudinal center plane are generally coplanar, and the second plane is offset from the longitudinal center plane. 
     
     
       28. The outboard motor as set forth in  claim 26 , wherein the engine additionally includes an ignition system firing the respective combustion chambers in a preset order, and the exhaust passages associated with the combustion chambers which have consecutive firing orders communicate with different ones of the exhaust manifolds. 
     
     
       29. The outboard motor as set forth in  claim 26 , wherein the cylinder bores and the exhaust manifolds have end openings facing in the same direction, and the cylinder head is coupled with the cylinder block in a manner cooperating with the end openings. 
     
     
       30. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including a cylinder block defining a plurality of cylinder bores and first and second exhaust manifolds extending next to the cylinder bores, the first exhaust manifold being interposed between the cylinder bores and the second exhaust manifold, the first exhaust manifold being longer than the second exhaust manifold, the cylinder bores and the first and second exhaust manifolds having end openings facing generally in the same direction, pistons reciprocating within the cylinder bores, and a cylinder head closing the end openings of the cylinder bores to define combustion chambers together with the cylinder bores and the pistons, the cylinder head further defining at least one exhaust port per combustion chambers and exhaust passages communicating with the exhaust ports, the exhaust passages being coupled with the first and second exhaust manifolds at the end openings of the first and second exhaust manifolds so that at least one of the exhaust passages is allotted to each one of the first and second exhaust manifolds. 
     
     
       31. The outboard motor as set forth in  claim 30 , wherein the end openings of the first and second exhaust manifolds are located generally on the same plane. 
     
     
       32. The outboard motor as set forth in  claim 30 , wherein the engine additionally includes an ignition system firing the respective combustion chambers in a preset order, and the exhaust passages associated with the combustion chambers which have consecutive firing orders communicate with different ones of the first and second exhaust manifolds. 
     
     
       33. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including an engine body defining a plurality of cylinder bores in which pistons reciprocate, the cylinder bores extending generally horizontally and spaced apart vertically from each other to form a cylinder bank extending generally vertically, the engine body further defining first and second exhaust manifolds, the first exhaust manifold being interposed between the second exhaust manifold and the cylinder bank, a top of the first exhaust manifold being positioned higher than a top of the second exhaust manifold, the engine body additionally defining exhaust passages communicating with the cylinder bores, and at least one of the exhaust passages being coupled with the first exhaust manifold, at least another one of the exhaust passages being coupled with the second exhaust manifold. 
     
     
       34. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including an engine body defining a plurality of cylinder bores, the cylinder bores disposed in line to form a cylinder bank, the engine body further defining at least two exhaust manifolds extending aside the cylinder bank, the engine body additionally defining exhaust passages communicating with the cylinder bores, the exhaust passages being coupled with the exhaust manifolds so that at least one of the exhaust passages is allotted to each one of the exhaust manifolds, pistons reciprocating within the cylinder bores, and a crankshaft coupled to the pistons and journaled for rotation about a crankshaft axis, and the cylinder bores and the crankshaft being arranged such that a first plane, which contains the crankshaft axis, lies parallel to and offset from a second plane, which contains axes of the cylinder bores, the first plane being offset to a side of the second plane on which the exhaust manifolds are disposed. 
     
     
       35. An outboard motor comprising an internal combustion engine and a support member arranged to support the engine, the engine including an engine body defining a plurality of cylinder bores in which pistons reciprocate, the. cylinder bores extending generally horizontally and spaced apart vertically from each other to form a cylinder bank extending generally vertically, the engine body further defining first and second exhaust manifolds extending aside the cylinder bank, the first exhaust manifold being interposed between the cylinder bank and the second exhaust manifold, a top of the first exhaust manifold being positioned higher than a top of the second exhaust manifold, the engine body additionally defining exhaust passages communicating with the cylinder bores, and at least one of the exhaust passages being coupled with the first exhaust manifold, at least another one of the exhaust passages being coupled with the second exhaust manifold, the first exhaust manifold including a downpipe section and a detour section that lies between one of the exhaust passages and the downpipe section.